What was puzzling is the the yml file only has 126 lines. I reran with the --debug and copied what looks like generated yaml, into np++. I joined up a few lines that had been split by the cmd window. Now, I had a final line 150!

At the time I created the backup statements I used a '/', but felt unsure that it would actually work when use to backup. I looked back in the yml file and saw that I have used a '\' for the location of the ssh keyfiles:

ssh-keyfiles:
- ..\..\ssh-keystore\dev411\mgmt.public.ssh.txt

So, I used a '\'

Putting the path in single quotes still failed on line 150. I changed to using '/' and the command worked.

I finally tried using '\\' Java-style and that parsed OK and the command ran.

Time will tell if this worked as intended. I can make mistakes on this system as it's a kind of sandbox running in Workstation and I have a backup of the VM.